Simple Determination of 1-Deoxynojirimycin in a New Dietary Supplement by Liquid Chromatography

A simple and fast chromatographic method using ultraviolet diode-array detector (UV-DAD) was developed for the high performance liquid chromatography determination of the content of 1-deoxynojirimycin (DNJ) in a new dietary supplement in the form of granules for oral solution preparation. The derivatization reaction was carried out at room temperature for 15 min at pH 7. The reaction reached completeness at a reagent to analyte molar ratio of about 60. The chromatographic separations were performed on a C18 Phenomenex Synergi Fusion stainless steel column (250 mm?×?4.6 mm; 4 µm) with detection at λ?=?254 nm. The mobile phase consisted of triethylammonium (TEA) phosphate buffer (0.05 M; pH 3) and acetonitrile under gradient conditions at a flow-rate ramping from 1 to 1.2 mL/min. The validation parameters (linearity, sensitivity, accuracy, precision, specificity and stability) were satisfactory. Intra-day precision (relative standard deviation, RSD) was ≤?2.23% for peak area and retention time without significant differences between intra- and inter-day data. Recovery studies gave good results (93.59%; n?=?15) with a RSD of 2.64%. The developed method is suitable for the quality control of DNJ in raw material and industrial products. The method can be applied in any analytical laboratory and does not require sophisticated instrumentation.     

Hierarchical MoS2@TiO2 Heterojunctions for Enhanced Photocatalytic Performance and Electrocatalytic Hydrogen Evolution

Hierarchical MoS₂@TiO₂ heterojunctions were synthesized through a one‐step hydrothermal method by using protonic titanate nanosheets as the precursor. The TiO₂ nanosheets prevent the aggregation of MoS₂ and promote the carrier transfer efficiency, and thus enhance the photocatalytic and electrocatalytic activity of the nanostructured MoS₂. The obtained MoS₂@TiO₂ has significantly enhanced photocatalytic activity in the degradation of rhodamine B (over 5.2 times compared with pure MoS₂) and acetone (over 2.8 times compared with pure MoS₂). MoS₂@TiO₂ is also beneficial for electrocatalytic hydrogen evolution (26 times compared with pure MoS₂, based on the cathodic current density). This work offers a promising way to prevent the self‐aggregation of MoS₂ and provides a new insight for the design of heterojunctions for materials with lattice mismatches.     

Bioorthogonal Catalytic Activation of Platinum and Ruthenium Anticancer Complexes by FAD and Flavoproteins

Recent advances in bioorthogonal catalysis promise to deliver new chemical tools for performing chemoselective transformations in complex biological environments. Herein, we report how FAD (flavin adenine dinucleotide), FMN (flavin mononucleotide), and four flavoproteins act as unconventional photocatalysts capable of converting Pt^IV and Ru^II complexes into potentially toxic Pt^II or Ru^II?OH₂ species. In the presence of electron donors and low doses of visible light, the flavoproteins mini singlet oxygen generator (miniSOG) and NADH oxidase (NOX) catalytically activate Pt^IV prodrugs with bioorthogonal selectivity. In the presence of NADH, NOX catalyzes Pt^IV activation in the dark as well, indicating for the first time that flavoenzymes may contribute to initiating the activity of Pt^IV chemotherapeutic agents.     

Non-destructive characterisation of the Elephant Moraine 83227 meteorite using confocal Raman,micro-energy-dispersive X-ray fluorescence and Raman-scanning electron microscope-energy-dispersive X-ray microscopies

Analytical and Bioanalytical Chemistry - The application of a non-destructive analytical procedure to characterise the mineral phases in meteorites is a key issue in order to preserve this type of...     

Propane oxidative dehydrogenation over V-containing mixed oxides derived from decavanadate-exchanged ZnAl–layered double hydroxides prepared by a sol–gel method

The catalytic properties of ZnAlVO mixed oxides derived from decavanadate-exchanged ZnAl–layered double hydroxide (LDH) precursors prepared by a sol–gel method (ZnAlVO–LDHx,y) were investigated in the oxidative dehydrogenation of propane and compared with those of supported catalysts obtained by conventional impregnation of NH₄VO₃ on ZnO (ZnVO-I,y) and ZnAlO mixed oxide (ZnAlVO-I,y) supports. The effects of composition and calcination time on the catalytic behavior were particularly examined. Higher propane conversions were achieved at higher vanadium content and calcination time of the precursors. The LDH-derived catalysts were the most active ones in all the temperature range studied (300–425 °C). The order of activity for propane conversion for the different catalyst families varies as ZnAlVO–LDHx,y > ZnAlVO-I > ZnVO-I and follows the strength of the Lewis and Brønsted acid sites determined by monitoring of pyridine adsorption by Fourier transform infrared spectroscopy, whereas the propene selectivities are close together in agreement with the similar densities of basic sites determined by CO₂–temperature-programmed desorption measurements. It was indeed established that the acidity, rather than the nature of the crystalline phases, the reducibility, or the specific surface area of the samples, governs the catalytic activity.     

An algorithm for computing minimal curves

Let ?³ be the 3-dimensional projective space over an algebraically closed field K of characteristic 0, and R be the graded polynomial ring K[x ₀,x ₁,x ₂,x ₃]. If C is a curve of ?³, let M _c := ⊕ H ^l I _C (n) be its Hartshorne-Rao module: it is a graded R-module of finite length which, up to a shift in degrees, characterizes the biliaison class of C. M. Martin-Deschamps &; D. Perrin (Sur la classification des courbes gauches. Astérisque 184–185 (1990)) have proved that in every biliaison class of non arithmetically Cohen-Macaulay curves there exists a minimal curve, unique up to a deformation with constant cohomology and Hartshorne-Rao module, that is a curve C such that, if C ₁ is any curve in the biliaison class of C, then M _{C 1} = M _c(?n), with n ≧ 0. They have moreover given an algorithm for the computation of a minimal curve, based on the computation and the analysis of the minors of given orders of some submatrices of the second syzygy matrix σ ₂ of M. The aim of this paper is to give an improvement to the algorithm for computing a minimal curve of a given Hartshorne-Rao module. The key remark is that the information obtained from σ ₂ can analogously be obtained from the matrix f(σ ₂) with entries in the polynomial ring K[u], where f:R → K[u] is a map which evaluates the variables of R to random linear polynomials in K[u]. The advantage of this approach is first, that the computations are done in a simpler polynomial ring and second, that in K[u]|we can take advantage of the Smith Normal Form algorithm to analyze the structure of the minors of the given matrices. The algorithm is therefore probabilistic but rather efficient and allows to compute (the invariants of) a minimal curve associated to modules whose syzygies matrices are considerably large. The algorithms presented here have been partially implemented and tested in the computer algebra systems CoCoA, Maple and Macaulay.     

Four N7‐benzyl‐substituted 4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐diones as ethanol hemisolvates: similar molecular constitutions but different crystal structures

3‐tert‐Butyl‐7‐(4‐chlorobenzyl)‐4′,4′‐dimethyl‐1‐phenyl‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione ethanol hemisolvate, C₃₀H₃₄ClN₃O₂·0.5C₂H₆O, (I), its 7‐(4‐bromobenzyl)‐ analogue, C₃₀H₃₄BrN₃O₂·0.5C₂H₆O, (II), and its 7‐(4‐methylbenzyl)‐ analogue, C₃₁H₃₇N₃O₂·0.5C₂H₆O, (III), are isomorphous, with the ethanol component disordered across a twofold rotation axis in the space group C2/c. In the corresponding 7‐[4‐(trifluoromethyl)benzyl]‐ compound, C₃₁H₃₄F₃N₃O₂·0.5C₂H₆O, (IV), the ethanol component is disordered across a centre of inversion in the space group P. In each of (I)–(IV), the reduced pyridine ring adopts a half‐chair conformation. The heterocyclic components in (I)–(III) are linked into centrosymmetric dimers by a single C—H...π interaction, with the half‐occupancy ethanol component linked to the dimer by a combination of C—H...O and O—H...π(arene) hydrogen bonds. The heterocyclic molecules in (IV) are linked into chains of centrosymmetric rings by C—H...O and C—H...π hydrogen bonds, again with the half‐occupancy ethanol component pendent from the chain. The significance of this study lies in the isomorphism of the related derivatives (I)–(III), in the stoichiometric hemisolvation by ethanol, where the disordered solvent molecule is linked to the heterocyclic component by a two‐point linkage, and in the differences between the crystal structures of (I)–(III) and that of (IV).     

Atomic decompositions for tensor products and polynomial spaces

We study the existence of atomic decompositions for tensor products of Banach spaces and spaces of homogeneous polynomials. If a Banach space X admits an atomic decomposition of a certain kind, we show that the symmetrized tensor product of the elements of the atomic decomposition provides an atomic decomposition for the symmetric tensor product , for any symmetric tensor norm μ. In addition, the reciprocal statement is investigated and analogous consequences for the full tensor product are obtained. Finally we apply the previous results to establish the existence of monomial atomic decompositions for certain ideals of polynomials on X.